Waveguides of various electrical characteristics are widely employed in the reception and transmission of electromagnetic waves. One of the many applications found for such waveguides has been missile systems in which size, weight and reliability are extremely important considerations.
While metal waveguides, such as disclosed in U.S. Pat. Nos. 2,592,614; 3,261,078, and 3,314,130 are suitable for many applications, their weight makes them unsatisfactory for missile applications. Thus, metal coated glass cloth, elastomer, and plastic waveguides such as described in U.S. Pat. Nos. 2,826,524; 3,290,762; and 2,870,524 have been developed.
When, however, it is desirable to utilize a waveguide as a frequency band pass filter, it is necessary that tuning posts be provided in the interior of the hollow waveguide. Conventional waveguide filters are heavy metal devices machined from aluminum, brass, or copper bronze alloys and containing numerous metal tuning posts. The tuning posts are normally made by inserting metal pins into the metal waveguide and soldering the pins in place. Besides being costly to machine, requiring close mechanical tolerances, and not being conducive to manufacture under production conditions, electrical manfunctions were rather common place from excess solder, pin displacement from soldering temperatures and tolerance error buildup.
With other than metal waveguides, no satisfactory method has been found to provide the tuning posts in the interior thereof. In addition those patents mentioned above the following patents were cited in U.S. Pat. Ser. No. 406,058: U.S. Pat. Nos. 3,713,051; 3,696,314; 1,485,061; 3,496,498; and Great Britain Pat. No. 798,519.